This invention is in the field of hand control valves; more particularly, the invention relates to a hand control valve having a unique clutch retention feature.
In the manual operation of various hand control valves, particularly hand control valves used in tractor-trailer vehicles, there is a requirement that the control lever or knob remain in the position selected by the operator. This can be accomplished by having a frictional element such as an O-ring between a stationary portion of the valve and a rotatable portion of the valve which is connected to the knob or lever. The stationary portion is forced against the frictional element which is in contact with the rotatable element so as to maintain the necessary frictional forces to maintain the set position of the hand control valve knob.
An early attempt to retain the setting of a globe valve is described in U.S. Pat. No. 72,868 in which a spring is attached at one end to a nonrotatable socket portion of the globe valve. The opposite end of the spring is attached to a friction clamp which is forced against the rotatable globe valve wheel or knob.
U.S. Pat. No. 2,711,191 discloses a spring biased against a rotatable washer which presses against a nonrotatable cap. There is not complete contact between adjacent surfaces of the washer and the cap. The cap has depressions into which bumps in the washer snap under the action of the spring to maintain the valve in its desired set position.
U.S. Pat. No. 2,510,393 discloses the use of a spring and washer combination in a cam valve to tend to close the valve. The spring operates to automatically maintain a rotatable washer in constant engagement with a nonrotatable washer. However, this arrangement tends to force the handle into a predetermined position rather than maintain it at any given set position.
Additionally of interest is U.S. Pat. No. 824,527 which shows the use of a spring mechanism to maintain a screw at a desired setting and U.S. Pat. No. 3,940,107 which discloses a rotary valve spring clutch.
There is a need to provide a means by which a hand control valve can be maintained at a particular setting. This is particularly important in cam-type valves in which fluid under pressure enters a chamber in the valve. In this case, there is a tendency for the valve to move in a direction to relieve the pressure. As noted, one way to maintain the valve in a desired set position is by the use of a frictional element such as an O-ring between rotatable and nonrotatable portions of the valve. However, in many operations an O-ring or similar elastomeric device does not exhibit constant properties with changing atmospheric conditions or exposure to wet, dry or oily environments. Further, the elastomeric-type frictional devices wear out. It is desirable to have a hand control valve having an improved clutch retention device to maintain it in a set position.